Charge forming apparatus



Feb. 22, 1966 B. c. PHILLIPS 3,236,505

A CHARGE FORMING APPARATUS Filed July 18, 1962 3 Sheets-Sheet l a 7INVENTORZ 526 48 L4 w w fimzzgzm [7. PHILLIPS.

4 I 3 g A I'TQRNEY Feb. 22, 1966 B. c. PHILLIPS CHARGE FORMING APPARATUS5 Sheets-Sheet 2 Filed July 18, 1962 7 7 5 5 MP W N. w M M 5 m QVA I 4Mm 5 m Mg B 0 6 24 fl AMA: M T. n I I M l W- f 2/ Q J a I d 6 5 Feb. 22,1966 c, PHlLLlPs 3,236,505

CHARGE FORMING APPARATUS Filed July 18, 1962 '5 Sheets-Sheet 5 IN VENTOR.

BERNARD [1. PHILLIPS.

United States Patent 3,236,505 CHARGE FORMING APPARATUS Bernard C.Phillips, Toledo, Ohio, assignor to The Tillotson Manufacturing Company,Toledo, Ohio, a corporation of Ohio Filed July 18, 1962, Ser. No.210,706 1 Claim. (Cl. 261-42) This application is a continuation-in-partof my application, Serial No. 51,414, filed August 23, 1960 and nowabandoned.

This invention relates to charge forming apparatus for supplying fueland air mixture to an internal combustion engine and more especially toa charge forming apparatus or carburetor embodying a flexible diaphragmarranged to be influenced or actuated by aspiration or reduced pressurein the mixing passage of the carburetor for automatically re gualtingthe deli-very of fuel from a supply into the mixing passage inaccordance with the requirements of the engine.

Charge forming devices or carburetors of the diaphragm type have beenemployed extensively for supplying combustible fuel and air mixture fortwo cycle engines of the types having particular utility for poweringchain saws, outboard motors, lawnmowers, air compressors, generators,ventilating fans, small portable engine operated equipment and wherevera diaphragm carburetor has been found to have utility.

An object of the invention is the provision of an arrange ment in acarburetor body fashioned of resinous plastic or of metal for ventingthe air space adjacent the diaphragm to avoid accumulation of fuel thatmay enter the space under certain operating conditions.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, operation and function of the relatedelements of the structures, to various details of construction and tocombinations of parts, elements per se, and to economics of manufactureand numerous other features as will be apparent from a consideration ofthe specification and drawing of a form of the invention, which may bepreferred, in which:

FIGURE 1 is a top plan view of a carburetor wherein the body member andother components are formed or fabricated of resinous plastic materials;

FIGURE 2 is a longitudinal sectional view of the carburetor, the sectionbeing taken substantially on the line 22 of FIGURE 1;

FIGURE 3 is a side elevational view of the carburetor illustrated inFIGURE 1;

FIGURE 4 is an elevational view of the air inlet end of the carburetorillustrated in FIGURE 1;

FIGURE 5 is a transverse sectional view taken substantially on the line5-5 of FIGURE 1;

FIGURE 6 is a detail sectional view taken substantially on the line 66of FIGURE 1;

FIGURE 7 is a sectional view taken substantially on the line 77 ofFIGURE 3;

FIGURE 8 is a longitudinal sectional view of a carburetor illustratingone form of venting arangement for the air space adjacent the diaphragm,and

FIGURE 9 is a sectional view of a diaphragm closure embodying a ventarrangement without a filter.

While the charge forming apparatus or carburetor of the presentinvention has particular utility for supplying combustible mixture toengines of the two cycle type, it is to be understood that thisinvention may be employed with four cycle engines. The charge formingapparatus or carburetor is particularly adaptable for use with internalcombustion engines for operating equipment such as marine motors,mowers, air compressors, generators, ventilating fans, power hammers andportable engine 3,236,505 Patented Feb. 22, 1966 ice operated equipmentand is usable wherever the carburetor is subjected to extreme positionsof tilt or inverted positions.

Referring to the drawings in detail the charge forming apparatus orcarburetor is inclusive of a body or a body member 10 formed or moldedof resinous plastic of nonporous character which is inert or resistantto deterioration by hydrocarbon fuels.

The body member 10 is molded or fashioned of a resinous plasticcommercially known as Delrin, identified chemically as polyoxymethylenewhich has high strength characteristics, is nonporous, and is highlyresistant to deterioration by hydrocarbon fuels. This material is ahighly crystalline thermo-plastic resin. The body member 10 is formedwith a mixing passage 12 which includes an air inlet region 14, aVenturi 16 having a choke band or region of restriction 1-8 and amixture outlet region 20.

The portion of the body 10 adjacent the air inlet region is formed withboss portions 22 bored to receive a shaft 24 journally mounted in thebores which supports a generally circular disc-type valve 26 as a chokevalve for starting the engine. The choke valve shaft 24 is integrallyformed with a manipulating arm 27 as a unit construction. The chokevalve shaft 24 and the arm 27 may be molded of polyoxymethylene(Delrin).

The body 10 is formed with boss portions 28 bored to journally receive ametal shaft 30 which supports a generally circular disc-type valve 32providing a throttle valve for regulating the flow of fuel and airmixture to an engine with which the carburetor may be used. An exteriorportion of the throttle shaft 30 is provided with a manipulating arm 34,an adjustable abutment screw 36 being supported by the body 10 andengageable with the arm 34 for adjusting the engine idling position ofthe throttle valve 32.

The carburetor body 10 is provided with a mounting flange 38 havingopenings 40 to accommodate bolts (not shown) for securing the carburetorto the crankcase of a two cycle engine or to an intake manifold of anengine of the four cycle type. A flange 42 adjacent the air inlet region14 is formed with threaded openings 44 to receive bolts or threadedmembers (not shown) for securing an air cleaner or air filter to thecarburetor body.

The body member 10 is fashioned with a shallow circular recess disposedin close proximity to the mixing passage 12 the recess providing a fuelchamber 46 adapted to contain liquid fuel. Extending across the fuelchamber 46 and forming a flexible wall of the chamber is a flexiblemember, diaphragm or membrane 48. The diaphragm 48 is preferably ofgenerally circular shape and is disposed adjacent a generally circularportion 52 of the body 10. An annular gasket 50 is disposed between thecircular portion 52 of the body and the peripheral region of thediaphragm 48. A closure or cover plate 54 embraces the exterior majorsurface of the diaphragm and is provided with openings which are inregistry with threaded bores in the annular portion 52 of the body 10 toaccommodate securing screws 56 which serve to secure the diaphragm 48,gasket 50 and closure plate 54 in assembled relation with the bodymember 10. The central region of the cover or closure plate 54 isdepressed or recessed providing a clearance space or chamber 58 toaccommodate flexing movements of the diaphragm.

The space or chamber 58 is vented to the air entrance end 14 of themixing passage by a tube 59 and registering passageways 60 and 61 asshown in FIGURE 2. If desired, the space or chamber 58 may be vented byeliminating the tube 59 and passageways 60 and 61 and providing anopening 63 illustrated in broken lines in FIGURE 2. The closure member54 may be molded 3 of polyoxymethylene (Delrin) or phenolformaldehyderesin (Bakelite).

The flexible diaphragm 48 is fashioned of a highly flexible, thinmaterial which is imperforate. The diaphragm may be made of resin filmcommercially known as KelF, identified chemically aspolytrifluorochloroethylene. This material has high strengthcharacteristics, will withstand elevated temperatures to about 200centigrade and is chemically inert to liquid hydrocarbon fuels. Thediaphragm may be made of polyvinyl fluoride film commercially known asTeslar. The diaphragm may also be made of a material commercially knownas Gentron which is identified chemically as chlorotrifluoroethylene.

The diaphragm 48 is reinforced by a disc-like member 62 formed of sheetmetal or molded resin and is disposed on the major surface of thediaphragm adjacent the chamber 4.6. A second circular disc-like member64 is disposed at the opposite side of the diaphragm, the discs 62 and64 being held in assembled relation with the diaphragm by a rivet 65 orother suitable means.

The diaphragm 48, in the embodiment illustrated in FIGURES 1 through 7is arranged to control the flow of liquid fuel into the chamber 4 6. Thecarburetor body is formed with a boss portion 66 provided with athreaded bore 67 accommodating the threaded portion of a fitting 68formed with a passage 69 to accommodate fuel flow. The fitting 68 isprovided with a nipple portion 70 which receives a flexible fuel supplyhose or tube (not shown).

The passage 69 in the fitting 63 is in communication with a chamber orpassage 72 formed in the carburetor body It), a screen or filter 74being disposed in the body adjacent the end of the fitting 68 forpreventing entrance of foreign particles into the carburetor body. Thebody 10 is provided with a threaded bore adapted to accom modate afitting or valve cage 76 having a central passage in which is slidablydisposed a valve body 78 formed with a cone-shaped valve portion 80; atone end thereof. An annularly shaped valve seat 82 is disposed at theend of the fitting and is adapted for cooperation with the cone-shapedvalve 86 to regulate or control fuel flow into the chamber 46.

Pivotally fulcrumed or supported upon a pin 84 is a lever member 86, thepin 84 being provided with a threaded portion 8'7 threaded into a borein the body 10 for securing the pin in position as shown in FIGURE 7.The long arm 88 of the lever 86 is adapted to be engaged by the head ofthe rivet 65 carried by the diaphragm 48, the short arm R of the lever86 engaging the lower end of the valve body 78 as shown in FIGURE 5. Thelever 86 may be molded of polyoxymethylene (Delrin). I

A11 expansive coil spring 92 is seated in a bore 93 formed in an upperwall of the fuel reservoir or chamber 46, as shown in FIGURE 5. Thespring engages the long arm 88 of the lever 86 and biases the lever formovement in a clockwise direction as viewed in FIGURE 5, which actionnormally urges the inlet valve 80 into seating position with the annularvalve seat 82 to interrupt fuel flow into the fuel chamber 46. While itis preferable to dispose the spring 92 close to the pivot pin 84 as itenables the use of a stiffer spring and obtain sensitive control of thediaphragm over the inlet valve 80, the spring may be positioned toengage any region of the lever arm 88. A

The fuel chamber 46 is unvented and the diaphragm is flexed solely byaspiration or reduced pressure in the mixing passage 12 set up by airflow through the mixing passage. A drain screw 96 is provided for thefuel chamber 46, shown in FIGURE 5, in the event that it is desired todrain fuel from the chamber 46.

Both the valve guide or cage 76 and the inlet valve member 78 may beformed or molded of polyoxymethylene (Delrin). The annular valve seat 82may be formed or molded of polytrifluorochloroethylene (KelF). The

utilization of a valve member or body 78 formed of molded plastic orresin attains several important advantages over the use of metals forthe valve member. For certain uses it is desirable to operate enginesand particularly two cycle engines at higher speeds upwards of 8000revolutions or more per minute.

Engine vibrations are necessarily transmitted to the carburetor body byreason of attachment of the carburetor directly to the engine. The inletneedle valve, which is subject to relative movement with respect to thecarburetor, is biased toward closed position by means of the expansivecoil spring 92, the valve being opened by upward flexure of thediaphragm 48 under the influence of aspiration in the mixing passage. Atcomparatively high engine speeds a metal valve body will not move orvibrate in synchronism with the carburetor and such outof-phasecondition results in the valve member or body not following themovements of the valve seat in the carburetor and remains open wherebyan excess amount of fuel flows into the carburetor impairing thefuel-air mixture ratio in the mixing passage. The spring 92 engaging thelever and biasing the inlet valve member toward closed position is apotential energy storage medium or reservoir. If the inlet valve isformed of relatively dense material such as metal, it may develop anasynchronous or out-of-phase bouncing movement relative to thecarburetor body under the influence of engine vibration, and thepressure or potential energy of the spring at certain engine speeds maynot be suflicient to overcome the inertia bouncing of the valve.

By utilizing a valve formed of plastic such as polyoxymethylene (Delrin)having a comparatively lowspecific gravity and therefore being but afraction of the weight of a valve member fashioned of stainless steel orbrass, the effect of engine vibration on the inlet valve at high speedsis greatly reduced and inertia bouncing eliminated so that an effectivecontrol or regulation of fuel flow into the carburetor is. attainedproviding for the delivery of a proper fuel and air mixture to theengine at high engine speeds.

It should be noted that the fuel chamber 46 is made as shallow as ispracticable and as close to the mixing passage 12 as is possible toreduce the amount of pneumatic lift required for fuel delivery andflexing the diaphragm 48. The upper Wall of the chamber 46 is fashionedwith a recess 98 of a configuration to accommodate pivotal movement ofthe lever 86 as shown in FIGURES 5 and 7.

The carburetor of the invention is inclusive of a main orificeconstruction which is fabricated as a removable unit 102 and a secondaryfuel delivery system including engine idling and low speed orifices 106and 108m facilitate idling of the engine and for low speed, engineoperation. The fuel conveying channels and adjustable fuel controllingor metering means for the main orifice and secondary orifice systemleillustrated in FIGURES 6 and 7. The main nozzle unit construction 102is pressed into a bore formed in the body lit in the position shown inFIGURES 1. and 6 whereby fuel for high speed engine operation isdelivered into the mixing passage in the zone of the choke band orrestricted region 18 of the Venturi construction.

The supplemental or secondary, fuel delivery system is inclusive of achamber 104 shown in FIGURES 2 and 7 from which the engine idlingorifice 106 and a low speed orifice 108 convey or deliver fuel into themixing passage adjacent the region of the throttle valve 32.

The fuel conveying channels and fuel regulating or metering means areillustrated in FIGURES 6 and 7. As will be noted from FIGURE 7, the axesof the fuel conveying channels are arranged in a single plane and arecontained in the circular disc-like portion 52 of the carburetor bodyproviding for a compact arrangement and small body construction.

Arranged in the disc-like portion 52 of the carburetor 5. body is apassage 111 as shown in FIGURE 7. Disposed axially of the passage andadjacent the high speed orifice construction 102 is a metal insert 110,preferably formed of brass. The insert or fitting 110 is formed with abore forming a continuation of the passage 111 and extending partiallythrough the insert, the insert having a restricted passage 114 incommunication with the passage 111 and a circumferential recess 166forming a fuel conveying channel in the body of the unit 102.

Disposed in the passage 111 is a high speed fuel metering valve body 112terminating in a needle valve portion 113, the needle valve portionextending into and cooperating with the restricted passage 114 providedin the metal fitting 110. As shown in FIGURE 6, the passage 111 is incommunication with the fuel chamber 46 by means of a passage 115 formedin a wall of the insert 110, the passage facilitates fuel flow from thefuel chamber 46 to the main orifice construction 102 and to thesupplementary or secondary fuel delivery orifices 106 and 108.

The valve body 112 has a threaded portion 116 cooperating with athreaded region in the wall of the passage 111, the valve body beingrotatable for regulating the position of the needle valve portion 113 toregulate or meter fuel flow to the main orifice construction 102. Thevalve member 112 is provided with a knurled knob 117 for adjusting theposition of the valve body 112. A sealing gasket 118 is disposed in acounterbore formed in the outer end region of the passage 111 forpreventing leakage of fluid along the valve member. A spring 119 engagesthe knurled knob 117 for exerting biasing pressure upon the seal 118 andsets up friction sufiicient to maintain the valve member 112 in adjustedposition.

Arranged in substantial parallelism with the passage 111 is a passage orduct 122. Disposed axially of the passage 122 is a metal insert 123. Theinsert or fitting 123 is formed with a bore forming a continuation ofthe passage 122 and extending partially through the insert. The insert122 is fashioned with a restricted passage 124 in communication with thechamber 104 of the secondary fuel delivery system. The passages 111 and122 are cored or molded into the carburetor body during the body moldingoperation. The passages 116 and 122 are in communication by means of apassage 130 and a restricted passage 132 as shown in FIGURE 7.

The passage 122 accommodates a valve member or body 134 terminating in aneedle valve portion 136 arranged for cooperation with the restrictedpassage 124 for metering or regulating fuel flow to the secondaryorifices 106 and 108.

The valve body 134 is provided with a threaded portion 138 threaded intoa bore in the body in axial alignment with the passage 122 for adjustingthe position of the needle valve 136. The valve body 134 is providedwith a knurled knob 140 for manipulating the valve body 134.

A sealing gasket 142 is disposed in a counterbore formed in the body andan expansive coil spring 144 engages the gasket and the knurled knob 140to bias the gasket into sealing engagement with the valve body andestablish friction for maintaining the valve body in adjusted position.As shown in FIGURE 2 the end of the bore forming the chamber 104adjacent the fuel chamber 46 is closed by means of a plug or cap 146.

From FIGURES 6 and 7, it will be seen that fuel flows from the chamber46 through the passage 115, passage 111, restricted passage 114 past theneedle valve 113 to the main orifice construction 102 for delivery intothe choke band region 18 of the Venturi 16. Fuel for the idle and lowspeed fuel delivery system flows from passage 111 through the passage130, past the needle valve thence through the restriction 124 into thechamher 104, which supplies fuel to the engine idling orifice 106 andthe low speed orifice 108, depending upon the relative position of thethrottle valve 32 and hence the velocity of air flow through the mixingpassage.

From FIGURE 7, it will be apparent that the needle valve 113 meters orregulates the fuel delivered to the main orifice construction 102, andthe needle 136 meters or regulates fuel flow into the chamber 104 forthe secondary orifices.

The carburetor of the invention is of a character which is operable invarious angular positions as well as inverted positions, conditionswhich are encountered Where the carburetor is used with engines poweringchain saws which must be adaptable for use in any position. In order tosecure satisfactory operation in all positions of the carburetor a checkvalve means is provided in the main orifice construction to prevent backbleeding of air from the mixing passage into the secondary orifice orfuel delivery system when the latter is in operation.

As particularly shown in FIGURES 2, 6 and 7, the main or primary nozzlearrangement and check valve means are constructed as a unit 102 whichmay be readily inserted and removed from a bore formed in the carburetorbody which opens into the mixing passage and into the diaphragm or fuelchamber 46. The nozzle unit is inclusive of a cylindrically shapedfitting or cage formed of metal such as brass or other suitablematerial. The fitting 150 is provided with an axial bore 152 which doesnot extend entirely through the fitting.

Arranged axially with the bore 152 is a counterbore 154 of slightlylarger diameter which accommodates a valve means such as a ball checkvalve 156. The passage 152 is of a diameter such that at the juncture ofthis passage With the counterbore 154, an annular seat is provided forthe check ball 156.

The counterbore 154 opens into the choke band 18 of the Venturi 16 andfunctions as the main or primary fuel delivery nozzle for high speedengine operation. The fuel delivery end region of the cage or fitting150 is provided with an abutment bar 158 for retaining the ball valve156 in the fitting 150.

The abutment member 158 is spaced above the ball valve 156 a sufficientdistance to facilitate movement of the valve away from its seat toprovide for fuel flow through passage 152 around the valve 156 and intothe mixing passage. The fitting 150 is provided with a circumferentialrecess 166 shown in FIGURES 2 and 7. The fitting 150 is provided withaligned transversely extending bores forming passages 168 whichestablish communication between the central bore 152 and the peripheralrecess 166 formed in the fitting.

The circumferential recess 166 is arranged so as to be in communicationwith the restricted passage 114. Thus during high speed engine operationfuel flows past the metering needle 113 enters the circumferentialrecess 166 thence through the passages 168 into the central bore 152,past the check valve 156 and is delivered or discharged from the fitting150 into the mixing passage.

The check valve 156 is preferably fashioned of lightweight material suchas nylon (polyamid resin) or Delrin (polyoxymethylene) requiring aminimum lift to elevate the ball from its seat. The relation between thediameter of the counterbore 154 and the diameter of the check ball 156is such that the annular region between the periphery of the ball andthe counterbore provides a cross-sectional area sufiicient to permit themaximum fuel flow required for high speed engine operation.

If it is desired to remove and replace the check ball and nozzleassembly 102, the fitting 150 may be driven entirely through the bore inthe body 10 to extrude the fitting into the Venturi and replaced byanother fitting assembly.

The lower portion of the fitting 150 is imperforate and forms, as a partof the fitting, a closure for the end of the bore adjacent the fuelchamber 46 as shown in FIGURES 2 and 6. FIGURES 1 through 7 illustratingthe carburetor are on a slightly enlarged scale for purposes ofillustration as the carburetor for use with engines of low horsepower issmaller than the scale shown in the drawings.

The operation of the charge forming apparatus or carburetor illustratedis as follows: As the fuel chamber 46 is unvented, the diaphragm isflexed or moved under the influence or aspiration or reduced pressureset up in the mixing passage by air flow therethrough. Reduced pressureelfective in the chamber 46 flexes the diaphragm upwardly as viewed inFIGURES 2 and 5 causing the lever 86 to be swung in a counterclockwisedirection as viewed in FIGURE 5 whereby the valve member 80 moves awayfrom its annular seat 82, facilitating fuel flow through the inletfitting 68 past the valve portion 80 along the facets of the valve body78 and into the chamber 46.

Fuel from the chamber flows through the recess 98, the restrictedpassage 114 past the high speed needle valve 112 through the circularrecess 166 and passages 168 into the central bore 152 past the ballcheck 156 and is delivered into the Venturi of the mixing passage 12 forhigh speed engine operation. Through the diaphragm control of the inletvalve, fuel flow past the inlet valve 80 is maintained to satisfy therequirements of the engine.

When the throttle is moved toward closed position, air velocity throughthe mixing passage decreases and the pressure increases in the fuelchamber 46 whereby, under the biasing pressure of the spring 92, thevalve 80 is moved toward closed position as the diaphragm 48 movesdownwardly as viewed in FIGURES 2 and 5.

Fuel for the idling and low speed orifices flows through passages 111,13%) and restricted passage 132, passage 122 past the needle valve 136into the chamber 104 If the throttle valve 32 is in engine idlingposition, fuel is delivered through the orifice 106., if the throttlevalve 32 is partially open fuel may be delivered through both orifices106 and 108. If the throttle is opened a greater distance the mainorifice comes into operation and the secondary orifices graduallydecrease fuel delivery into the mixing passage.

When one or both secondary orifices 106 and 108 are delivering fuel intothe mixing passage and fuel ceases flowing into the mixing passagethrough the main orifice unit 102, the check Valve 156 is seated toblock the flow of air from the mixing passage through the main nozzleand thus prevent air bleeding into the fuel conveyed to the chamber 164for delivery to the secondary orifices.

The passages 107 and 130, shown in FIGURE 7 may be cored or formed inthe body during the molding thereof and are utilized to accommodateadjustable fuel metering valves similar to the valves 116 and 138 whereinstallation conditions render it desirable that access to the fuelmetering adjusting means be provided at the air entrance end of thecarburetor.

Several advantages are attained by molding the carburetor body 10, theinlet valve body 78, the closure plate 54, the lever 86, and the chokevalve shaft 24 and its manipulating portion 27 from polyoxymethylene(Delrin). By fashioning the body 10 of this resin, the resin is endowedwith heat insulating characteristics which prevent or deter thetransmission of heat from the engine to the fuel in the carburetor bodyand hence the liability of vapor lock or premature volatilization of theliquid fuel in the carburetor is substantially eliminated. Several ofthe channels or passages in the carburetor body may be formed during themolding operation with a high degree of accuracy eliminating manymachining or fabricating operations. Where machining is necessary, theresin may be readily machined or worked with a minimum of Wear of thetools. The dies for molding the resin have much longer life than diesused for molding or casting carburetor bodies of metal or metal alloys.

The inlet valve body 78 formed of resin is of light weight, which ashereinbefore explained provides for more accurate metering or regulationof fuel flow into the carburetor particularly at high engine speeds. Thevent passages and openings for accommodating screws in the closure plate54 may be formed during molding thus eliminating machine work on thiscomponent. The shaft 24 and the manipulating arm 27 molded as a uniteliminates machine and assembly operations heretofore necessary when theshaft and arm are fashioned of metal.

The metal inserts or fittings and 123 are accurately positioned in themolding die and are embedded in the resin by the molding operation. Theweight of the carburetor assembly with the body and above-mentionedcomponents formed of molded resin is substantially less than a similarassembly where the body and components are made of metals such asaluminum, aluminum alloys, zinc or zinc alloys. Thus, in addition to asubstantial reduction in weight, extensive savings in labor and machineoperations are eifected whereby the cost of producing the carburetor isgreatly reduced.

FIGURE 3 illustrates a carburetor embodying a venting means for the airchamber adjacent the diaphragm. The carburetor body 10' shown in FIGURE8 may be fashioned of resinous plastic material of a charactercommercially known as Delrin or the like, or the carburetor body may 'befashioned of metal. The body 10' is formed with a mixing passage 12which includes an air inlet region or air horn 14, a Venturi 16' havinga choke 'band or zone of restriction 18 and a mixture outlet region 20.

The body 10' adjacent the air inlet region is bored to receive arevoluble shaft 24 supporting a disc-type choke valve 26'. The body 10'at the mixture outlet region is bored to accommodate a revoluble shaft3% supporting a disc-type throttle valve 32'. The carburetor body isfashioned with a mounting flange 38 for securing the carburetor to acrankcase of a two cycle engine or to an intake manifold of a four cycleengine. A flange 42' adjacent the air inlet region 1% is adapted tosupport an air filter or air cleaner so that air entering the inlet 14is filtered.

The body 10 is fashioned with a shallow circular fuel chamber 46 adaptedto contain liquid fuel. Extending across the fuel chamber 46' andforming a flexible wall of the chamber is a flexi'ble diaphragm 48 anannular gasket 50' being disposed between the diaphragm and thecarburetor body. A closure or cover plate 174 embraces the exteriormajor surface of the diaphragm and is secured to the carburetor body byscrews in the manner illustrated in FIGURE 3. The central region of thecover or closure plate 174 is depressed or recessed providing aclearance space or air chamber 176 to accommodate flexing movements ofthe diaphragm.

The carburetor illustrated in FIGURE 8 embodies a fuel inlet valvearrangement of the character illustrated in FIGURE 5 wherein a member 65carried by the diaphragm cooperates with a lever 86 whereby theaspiration in the fuel chamber 46 controls fuel flow from a supply intothe fuel chamber. The carburetor shown in FIG- URE 8 is inclusive of amain orifice construction fabricated as a unit 102 and a secondary fueldelivery system including an engine idling orifice 106' and a low speedorifice 168' to facilitate idling of the engine and for 'low speedengine operation.

The adjustable controlling or metering means for the main orifice andsecondary orifice system are of the character illustrated in FIGURES 6and 7.

The main orifice unit 102 is inclusive of a cylindricallyshaped fittinghaving a main orifice or outlet 154 and a valve means such as a ballcheck valve 156 to prevent back bleeding of air through the main orificewhen the secondary orifice system is delivering fuel into 9 ing fuelfrom the fuel chamber 46 to the main orifice construction unit 102' areillustrated in FIGURES 6 and 7.

The diaphragm closure plate 174 may be fashioned of resinous plasticmaterial or may be formed of metal. The walls 178, defining a depressedregion of the closure plate, are slanted downwardly or in convergingrelation as shown in FIGURE 8, and terminate in a central circular wall180 which is slightly depressed to form a sink or recess 182 in whichmay accumulate any fuel which enters the air chamber 176. The wall 180is provided with a comparatively small size vent opening 184 which isvented to the atmosphere.

The plate 174 is fashioned with a depending skirt portion 186 defining arecess or chamber in which is disposed a filter 188. The filter may beformed of felt or other suitable filter material so that air enteringthe vent 184 into the space 176 is filtered to avoid the entrance ofdust or foreign matter into the chamber. The chamber 176 is also ventedto the air inlet region 14 of the carburetor through interconnectingducts 190 and 192 formed respectively in the plate 174 and thecarburetor body and a tubular member 194 in communication wtih the duct192 which opens into the air inlet region 14. The interconnecting ducts190, 192 and the tubular member 194 forming an S-shaped passageway withthe bottom and top portions of the S being upwardly inclined from theair chamber 176 and the central portion of the S being verticallyinclined as best shown in FIGURE 8.

Under normal operating conditions with an air filter or air cleanerdisposed at the entrance of the air inlet region 14, the tube 194- willbe under slight subatmospheric pressure due to the resistance of airfilter to the passage of air. It should be noted that the vent 184 issubstantially smaller than the vent provided by the ducts 190, 192 andthe tube 194 so that while the tube 194 is under slight subatmosphericpressure, the vent 184 is at atmospheric pressure and hence, duringengine operation, there will be a slight, though continuous, flow of airthrough the vent filter 188, the vent 184 and through the connectingducts 190, 192 and the tube 194 into the mixing passage.

The venting arrangement shown in FIGURE 8 prevents the accumulation ofliquid fuel which may enter the air chamber 176. Sometimes under r-amreaction in the mixing passage or possibly due to over-choking of theengine by manipulation of the choke valve 26', fuel from the mixingpassage may enter the tube 194 and flow into the chamber 176' and mayaccumulate to an extent that it would cause a hydraulic lock beneath thediaphragm. Through the provision of the venting arrangement shown inFIGURE 8, fuel which enters the chamber 176 through the vent tube 194and the interconnecting ducts will flow into the sink or depression 182and drain off through the vent opening 184.

With the arrangement shown in FIGURE 8 under normal engine operation, aslight, but continuous air flow inwardly through the vent 184 into theair inlet region 14 through the tube 194 occurs as above mentioned sothat there will be no accumulation of fuel in the chamber 176.

The use of the filter 188 is desirable as, during normal engineoperation, air will enter the small vent 184 in the manner described andthe filter 188 prevents the ingress of any foreign matter into thechamber 176.

Due to the difierence in size of the vent 184 and the vent arrangementthrough the tube 194, a very slight subatmospheric pressure is existentin the air chamber 176 during normal engine operation, to obtain abetter balance of pressures than in the arrangement shown in FIGURE 2wherein a venting of the chamber 58 is solely through the tube 59opening into the air inlet region 14.

FIGURE 9 illustrates a modified form of closure plate for the diaphragm.In this form, the closure plate 198 is fashioned with downwardlycoverging walls 200 and are joined with a central wall portion 202providing a sink or recess 204. In this form the vent opening 184 isdirectly to the atmosphere without the use of a filter. The air chamber176 is also vented to the air inlet region of the mixing passage througha duct which interconnects with ducts 192 and 194 of the character shownin FIGURE 8.

It is apparent that, within the scope of the invention, modificationsand different arrangementsmay be made other than as herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

I claim:

In combination, charge forming apparatus including a body member formedwith a fuel and air mixing passage and a comparatively shallow fuelchamber, a choke valve in the inlet region of the mixing passage, aflexible impervious diaphragm forming a wall of the fuel chamber, a fuelinlet for the fuel chamber, a valve for said inlet, motion transmittingmeans between the diaphragm and the inlet valve whereby movement of saiddiaphragm controls said inlet valve to regulate flow of liquid fuel froma supply into the fuel chamber, resilient means normally biasing theinlet valve toward closed position, orifice means opening into themixing passage arranged to deliver fuel from the fuel chamber into themixing passage, a closure for said diaphragm having an air chamberformed therein accommodating movement of the diaphragm and wall regionsopposite the diaphragm; said closure, said fuel chamber and saiddiaphragm being in stacked relation and secured directly below said airmixing passage; the wall regions opposite the diaphragm being in stackedrelation and secured directly below said air mixing passage; the wallregions opposite the diaphragm defining the air chamber being downwardlycovergent and terminating in a centrally disposed relatively shallowrecess, a first vent opening centrally located in the wall regiondefining the recess, said closure being formed with a downwardlyprojecting skirt portion adjacent said first vent opening, a filterelement disposed adjacent the first vent opening and within said skirtportion whereby air entering said first vent opening passes through saidfilter, a second vent opening between the air chamber and the air inletregion of said mixing passage, said first vent opening being of smallercross-sectional area than the second vent opening, said second ventopening being connected to an S-shaped passageway, the bottom portion ofsaid S-shaped passageway being inclined upwardly from said second ventopening, the central portion of said S-shaped passageway connecting saidbottom portion and extending in a vertical direction, and the topportion of said S-shaped passageway inclined upwardly from said centralportion and including a vent tube projecting at an angle into saidmixing passage and in advance of said choke valve.

References Cited by the Examiner UNITED STATES PATENTS 2,683,027 7/1954Garretson 26l16 2,728,564 12/1955 Bracke 261-69 2,733,902 2/ 1956Phillips. 2,796,838 6/1957 Phillips 261--35 2,918,046 12/1959 Teagarden26l69 3,000,320 9/1961 Ring 103-150 OTHER REFERENCES Injection Moldingof Delrin, E. I. du Pont de Nemours and Co., Wilmington 98, Delaware,Copyright 1958, page 6 relied on.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner.

